M&R Session 3 and 4 Flashcards
(142 cards)
How is membrane potential measured?
Potassium chloride filled microelectrode penetrates cell membrane conducting its potential
What is the basis of signalling in many types of cell?
Electrical potential difference across the plasma membrane
How is resting membrane potential expressed?
Potential inside relative to potential of solution outside
In mV
What is the range of resting potential in animal cells?
-20 to -90 mV
What is the resting potential of cardiac muscle?
-80 mV
What is the resting potential of skeletal muscle?
-90 mV
What range does the resting potential of nerve cells lie within?
-50 to -75 mV
What is the approximate resting potential of smooth muscle?
-50 mV
What are ion channels?
Proteins with an aqueous pore which enables ions to cross cell membranes
Give three properties of ion channels.
Selectivity for 1/a few ions
Gating by conformational change
Rapid ion flow always down electrochemical gradient
What dominates the membrane ionic permeability for most cells at rest?
Open voltage-insensitive potassium channels
What must be equal and opposite for no net movement of ions across a cell membrane?
Electrical gradient
Chemical gradient
In a resting cell, are the anion channels open or closed?
Closed
Permeability to which ions establishes the membrane potential?
Potassium
What assumptions are made when using the Nernst equation?
Membrane perfectly selective for the ion
Temperature is 37 degrees Celsius
Pressure is standard
What is ‘z’ in the Nernst equation?
Valency (charge)
Describe the behaviour of sodium and calcium channels in the resting cell membrane.
Closed but not perfectly - allow enough ions in to depolarise to -70 mV
What makes skeletal muscle cells have a more negative resting potential?
Chloride channels
Which ion equilibrium potential are cardiac and nerve cells close to?
Potassium
What causes cells to have a higher resting potential?
Lower selectivity for potassium
Increased contribution from other ion channels
Which two equilibrium potentials are skeletal muscle cells close to?
Chloride
Potassium
What is changing membrane potential used for?
Action potentials in nerve and muscle cells
Triggering of muscle contraction
Postsynaptic actions of fast synoptic transmitters
Control of neurotransmitter and hormone secretion
Transduction of sensory input to electrical activity
Define depolarisation.
Decrease in size of membrane potential from normal value
Cell interior becomes less negative
Define hyperpolarisation.
Increase in size of membrane potential from normal value
Cell interior becomes more negative